1. Field of the Invention
The present invention relates to an endoscope treatment instrument that is a treatment instrument employed in combination with a flexible endoscope for example, this endoscope treatment instrument being provided with a sheath that has both the property of rotational follow-up as well as the characteristics required of a sheath equipped with a treatment portion.
2. Description of Related Art
Endoscope treatment instruments that are employed by insertion into the channel of a flexible endoscope conventionally include such examples as dissection instruments, grasping forceps, etc. In such endoscope treatment instruments, various treatment portions such as a forceps cup or jaws, or an electrode part composing a dissection part etc., are formed at the distal end of a flexible sheath. As a method for adjusting the orientation of the treatment portion in these endoscope treatment instruments, the proximal end of the sheath is rotated and this rotational force is transmitted via the sheath to the treatment portion at the distal end, thereby rotating the treatment portion.
In the endoscope treatment instrument disclosed in Japanese Patent Application, First Publication No. 2000-229084, for example, an operating wire is inserted into an entire length of the flexible sheath that is inserted into a channel, a forceps cup which can be opened and closed is provided to the distal end side of the operating wire, and an actuator is provided at the proximal end side of the operating wire. The sheath is formed of a multiple layer coil in which two coil pipes which is wound in opposite directions and is overlapped each other. The proximal end of the sheath is fixed in place to the actuator. By rotating the rotation operating pin of the actuator in the axial direction of the sheath, the operating wire and the sheath rotate, so that the forceps cup rotates in the axial direction of the sheath.
The device disclosed in Japanese Patent Application, First Publication No. Hei 3-47246 is provided with a sheath consisting of a flexible and tightly wound coil, a treatment portion such as a biopsy cup provided at the distal end of the sheath, and an actuator which is provided on the handheld side of the sheath. In this device, the movement of the actuator is transmitted to the treatment portion via an operating wire which is inserted into the sheath. The sheath is provided with three types of tightly wound coils: a single strand apex coil, a single strand intermediate coil that has a thicker diameter than the apex coil, and a multiple strand rear end coil. The hardness of the sheath gradually increases from the apex to the rear. Further, by sliding the slider that is provided to the actuator forward and back, a treatment portion can be opened or closed. In addition, the sheath rotates by rotating the actuator for the treatment instrument, thereby enabling the orientation of the treatment portion to be changed.
As a method for adjusting the orientation of the treatment portion that is provided to the distal end of the sheath in these endoscope treatment instruments, the actuator and the proximal end of the sheath are rotated, and this rotational force is transmitted to the treatment portion via the sheath, thereby adjusting its orientation.
However, a sheath equipped with a treatment portion is typically required that the distal end part (within the range of 200 mm from the proximal end of the treatment portion, for example) which overlaps the bending part of the endoscope, be flexible. For this reason, a design in which a multiple layer coil is employed over the entirety of the sheath; a design in which a single strand apex coil, a single strand intermediate coil with a wider diameter than the apex coil, and a multiple strand rear coil are connected so that the hardness gradually increases from the distal end to the proximal end of the sheath; or a design in which a regular single strand coil is connected to the distal end of a multiple strand coil; such as described above, are employed.
However, in a sheath in which the entirety of the sheath consists of a multiple layer coil, since whole of the sheath is flexible, the rotation follow-up property of the sheath is good but the response of this sheath is poor when advancing or retracting the sheath. Further, in the case of sheaths in which a single strand intermediate coil and a multiple strand rear coil are connected so that the hardness gradually increases from the single strand coil provided at the distal end, toward the proximal end side, and sheaths in which a regular single strand coil is connected to the distal end of a multiple strand coil, the excellent rotation follow-up property of the multiple strand coil is nullified by the poor rotation follow-up property of the single strand coil portion at the distal end in these cases.